1. Field of the Invention
The present invention relates to a recording tape cartridge in which a single reel, on which is wound a recording tape such as a magnetic tape mainly used as a recording and playback medium for a computer or the like, is accommodated in a case.
2. Description of the Related Art
A recording tape cartridge, in which a recording tape such as a magnetic tape used as a recording and playback medium for a computer or the like is wound on a reel, and the reel is rotatably accommodated in a case formed from a plastic material, is conventionally known. The recording tape cartridge is arranged such that when in use (when loaded into a drive device), the reel is rotatable in the case, while when not in use (when not loaded into a drive device), the reel is locked so as to be non-rotatable in the case.
More specifically, the recording tape cartridge is provided with braking means for preventing the reel from being rotated within the case when the cartridge is not in use. The braking means may be constructed such that, for example, a brake member which is non-rotatable with respect to the case can be engaged with the reel.
As shown in FIG. 19, for example, a brake member 200 is configured in the form of a disk which is accommodated so as to be vertically movable within a bottomed cylindrical shape reel hub 204 of a reel 202. A pair of engagement projections 206 which are each substantially U-shaped as seen in plan view are provided upright on the upper surface of the brake member 200. A pair of rotation regulating ribs 210 suspended from the inner surface of an upper casing 208 are inserted inside the engagement projections 206, making the brake member 200 non-rotatable with respect to the case 212.
Further, the brake member 200 is normally biased toward a bottom wall 216 of the reel hub 204 with the aid of a biasing member such as compression coil spring 214, so that an annular brake gear 218 formed in the lower surface of the brake member 200 is meshed with an annular engagement gear 220 formed in the upper surface of the bottom wall 216 of the reel hub 204. In this manner, the reel 202 is prevented from inadvertent rotation.
Still further, a substantially cylindrical operation projection 222, which is provided so as to protrude at an axial center portion of the brake member 200, is inserted into a through hole 216A formed in an axial center portion of the bottom wall 216 of the reel hub 204, and faces a gear opening 226 formed at a substantially center portion of a lower casing 224. When making the reel 202 rotatable, the operation projection 222 (brake member 200) is pushed upward, and as a result the brake gear 218 is disengaged from the engagement gear 220 (see, for example, U.S. Pat. No. 6,452,747).
However, with the above-described arrangement, when the recording tape cartridge is not in use, since the reel 202 is movable upward (movable in an axial direction of the reel 202) against a biasing force of the biasing member such as compression coil spring 214, it has happened that when the bottom wall 216 of the reel hub 204 is moved upward because of the recording tape cartridge being impacted due to being dropped or the like, the brake member 200 becomes tilted and jammed at the edge of the through hole 216A while remaining in a tilted orientation, as shown in the drawing.
If the recording tape cartridge is loaded into a drive device in such a condition, the problem exists that either recording/playback can simply not be performed or, moreover, that the recording tape cartridge is damaged or the drive device malfunctions. A further problem is that since the reel becomes rotatable when not in use, the recording tape tends to become wrinkled or is torn.